The purpose of this proposal is to extend our research on the organization of the olfactory system in two new directions at the level of local circuits. One of these involves the development of in vitro preparation of the turtle olfactory bulb and olfactory tubercle. The use of slice preparations combined with Nomraski microscopy will permit extra and intracellular unit analysis of relay neurons and interneurons under stable and chemically-defined conditions. The second involves the development of computer models of olfactory bulb neurons, based on the compartmental methods of Rall. This will build on previous studies in the motoneuron and the olfactory bulb, as well as recent studies in other systems. The physiological and computational studies will run in parallel, and will provide for rigorous testing of hypotheses related to neuronal properties and synaptic interactions. The results should be especially useful in clarifying the roles of reciprocal synapses and graded dendritic potentials in information processing by local circuits.